South Korea’s president said Monday that there are signs that North Korea is preparing for a fifth nuclear bomb test amid reports of increased activity at the country’s main nuclear test site.

In a regular meeting with her top adviser, President Park Geun-hye said that North Korea could carry out such a test to try to bolster morale as the country deals with tough international sanctions imposed after it conducted a fourth nuclear test and a long-range rocket launch earlier this year.

Park didn’t elaborate on what signs pointed to another nuclear test, but ordered the military to be ready to deal with any provocation by Pyongyang, according to media pool reports on the first part of the meeting posted on the website of her office.

Speculation about a fifth nuclear test increased last month when the North’s state media cited leader Kim Jong Un as ordering a test of a nuclear warhead and ballistic missiles capable of carrying warheads.

Kim’s order came amid rising animosity with South Korea and the United States over their annual military drills that North Korea describes as an invasion rehearsal. The drills are set to run until next week.

Analysts say an atomic test could happen before North Korea holds a landmark ruling Workers’ Party congress in early May so that Kim can burnish his image as a powerful leader at home and further cement his grip on power.

South Korea’s Yonhap news agency said Monday that South Korean and U.S. authorities detected two to three times more vehicle and personnel activities than normal this month at the North’s northeast Punggye-ri nuclear test site — where all previous four bomb tests took place.

A U.S. website that monitors sensitive sites in North Korea said Friday that it saw further signs from satellite imagery that the North was looking to produce more plutonium for nuclear weapons at its main Nyongbyon nuclear complex, north of Pyongyang.

Earlier last week, the website 38 North said recent satellite imagery of the Punggye-ri area showed little evidence that Pyongyang was planning a nuclear test, though it added that the country may be able to carry out a test on short notice.

Foreign experts said that a fifth test could put North Korean scientists and engineers a step closer toward a goal of manufacturing a warhead small enough to place on a long-range missile that could reach the U.S. mainland.

South Korean defense officials say North Korea currently does not have a reliable intercontinental ballistic missile, although it has made strides in its weapons development programs in recent years.

Last Friday, a North Korean missile launch meant to celebrate the birthday of Kim Il Sung, North Korea’s founder and Kim Jong Un’s late grandfather, ended in failure, according to U.S. officials. South Korean media reports said the failed missile was a new, powerful mid-range missile that could theoretically place U.S. military bases in Asia within reach.

(AP)